Mining, perhaps more than other industries because of its antiquity, tends to use rather arcane terminology — drifts, raises, highwalls, hanging-walls, stopes, cross-cuts, etc. Therefore there is an additional layer of miscommunication possibilities, and we need to also consider this vocabulary. As applied to mine waste, mining vocabulary falls into two main categories — tailings and waste rock:
Tailings — fine grained, well sorted (i.e. poorly graded) residues from ore processing, deposited underwater in impoundments. Some have been ground to sand size whereas others are silt-clay size and constitute the tailings class referred to as slimes. Most, but not all, of the ore metals have been removed, but appreciable pyrite or arsenopyrite content may remain. Therefore, if exposed to oxygen, tailings can release large amounts of acid, arsenic and heavy metals. Because of their small grain size, lack of plant nutrients, phytotoxic metals, and huge total volume, tailings constitute one of the most significant operating and post-closure challenges to sustainable mining (see e.g. Vick, 1983, chapter 12; ICOLD 1996a, 1996b; Szymanski, 1999).
Waste rock — large pieces of unprocessed, poorly sorted rock derived from overburden in open pit operations or low-grade portions of the orebody in underground operations. Waste rock is deposited above-ground in large piles or tips, sometimes referred to in coal mining as gob piles. This material is often highly pyritic and hence a source of acid drainage. Waste rock piles can be so large in volume that they come to dominate the local landscape. Long-established mining communities come to regard them as natural features of the terrain and may resist their removal. Waste piles tend to have very acid soil and experience high internal temperatures from pyrite oxidation, making revegetation difficult, and they pose a significant hazard from slope failure. In copper and gold mines, waste rock piles are commonly leached with acids or cyanide to improve recovery and these “heap leach” piles pose their own stability and reclamation problems (Earley et al., 2003).